MRI Interference Frequency Avoidance via Pre-calculation
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Solution Overview
Problem
Magnetic resonance scanners face challenges with interference frequencies that lead to excessive excitations, noise, and heating issues, limiting the freedom of scanning protocols and increasing scanning times, as existing solutions like passive frequency monitors are inefficient and unpredictable.
Innovation Solution
An active frequency monitor system that includes a limitation supply processor, simulation processor, and checking processor to pre-calculate and check scanning protocols against interference frequency limitations, preventing excessive excitations by determining a temporal control sequence and evaluating the frequency spectrum, and automatically adjusting recording parameters to avoid interference frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passive frequency monitor is implemented to stop scans when interference frequencies are detected, then excessive excitations in interference frequencies are avoided, but scanning time is lost and workflow is significantly impeded
Solution Approach 1:
The system performs preliminary calculation of the frequency spectrum before the actual scan is executed. The simulation processor calculates the frequency spectrum based on the scanning protocol parameters, and the checking processor verifies whether interference frequencies will be excited. This preliminary check prevents unnecessary scan execution that would result in time loss, while still ensuring that excessive excitations are avoided.
2Reliability
If interference frequencies are prohibited outright in scanning protocol design, then excessive excitations are prevented, but freedom of definition of scanning protocols is severely limited
Solution Approach 1:
The system provides feedback to the user about which specific recording parameters cause excessive excitations in interference frequencies. The checking processor identifies the problematic parameters and communicates this information back, allowing the user to adjust only the necessary parameters while maintaining freedom in defining other aspects of the scanning protocol. This selective feedback approach prevents excessive excitations without severely limiting protocol design freedom.
3Productivity
If minimal frequency limitations are imposed on the magnetic resonance scanner, then scanning workflow is maintained, but excessive excitations in interference frequencies cannot be avoided
Solution Approach 1:
The system dynamically evaluates recording parameters against frequency limitations specific to each scanner configuration. Instead of imposing minimal or fixed frequency limitations, the checking processor calculates the actual frequency spectrum based on the specific scanning protocol and compares it against the scanner's interference frequency characteristics. This parameter-based approach maintains workflow efficiency by allowing scans that meet the specific frequency criteria while preventing excessive excitations when limitations are violated.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables early recognition and avoidance of excessive excitations, reducing scanning time losses and improving workflow by ensuring compliance with interference frequency limits, thereby maintaining scanner stability and efficiency.
Implementation Method 1
Different frequencies can be generated by the physical gradient axes of the gradient coils of the gradient coil arrangement as a function of the scanning sequence that is used, recording parameters, and forms of the gradient pulses in the time domain
Implementation Method 2
the spectral distribution of the corresponding frequencies has no effect on the hardware of the magnetic resonance scanner. Particular frequency bands can excite acoustic resonances and therefore lead to increased noise in the magnetic resonance scanner
Implementation Method 3
magnetic gradient fields are used that are generated by appropriate gradient coils of a magnetic resonance scanner
Implementation Method 4
Magnetic resonance imaging uses a strong magnetic field, for example of 1.5 tesla or 3 tesla, so nuclear spins in a subject orient themselves along this basic magnetic field (B0)
Implementation Method 5
These uniformly aligned nuclear spins are excited by radio-frequency pulses and the decay of this excitation can be measured
Implementation Method 6
Frequencies of this kind, which can lead to undesirable, interfering effects in the magnetic resonance scanner, will be called interference frequencies hereinafter, and these can also lie in interference frequency bands. These excitations can lead to increased heating inside the basic field magnet, which can cause a coolant, in particular helium, used for cooling the basic field magnet to evaporate
Data Source
AI summary
In a magnetic resonance apparatus and an operating method therefor, at least one limitation criterion, which describes the avoidance of excessive excitations in an interference spectrum in the magnetic resonance scanner of the apparatus, formed by an interference frequency or an interference frequency range, is specified by a limitation supply processor in order to check a scanning protocol, described by recording parameters, that is to be implemented. At least part of the temporal control sequence of the scanning protocol is determined as a pre-calculation sequence from the recording parameters by a simulation processor and the pre-calculation sequence is checked in a checking processor by the limitation criterion. Implementation of the scanning protocol is prevented when the limitation criterion is not fulfilled.